Various types of conduits such as those used in underground sewer systems, require occasional treatment for various purposes. For example, it may be necessary to dispense foaming fumigants in the conduit to kill roots or other plant growth, or it may be necessary to apply corrosion retardants, grease removal agents, paint, and other types of material to the inner surface of the conduit.
One method that has been employed for treating the interior of closed conduits such as underground sewer systems involves manually feeding a hose into the closed conduit in the downstream direction and then withdrawing the hose from the conduit in the upstream direction while the material for treating the interior of the conduit is pumped through the hose.
In another method, a tagline is floated downstream behind a parachute or other type of float. The tagline is then used to pull the hose through the conduit. After being pulled to the desired point, the hose is withdrawn while the treatment material is dispensed.
Another method involves a fluid jet which is connected to the leading end of the hose. When the jet is turned on, the force of the jet propels the hose in the direction opposite to the direction in which the jet is pointing. Thereafter, the hose can be withdrawn while the treatment material is applied. However, several problems exist with the aforementioned methods.
By way of example, the access openings or manhole covers to the conduits through which the hose is fed are spaced apart a significant distance from one another, usually at intervals of 250 to 500 feet. The common practice is to treat or apply material to the conduit from one manhole cover to the next. When the hose is forced into the conduit manually, a significant amount of manual labor is required to push the hose through the conduit and then withdraw the hose for application of the treatment material. In addition, manually pushing the hose through the conduit can be quite time consuming.
Another problem concerns the friction build-up that occurs as more and more hose is fed into the conduit. While it may be readily easy to push an initial portion of the hose into the conduit, as more and more hose is fed into the conduit and pushed along the inner surface of the conduit, a frictional force is built up which causes further difficulty in attempting to push the hose the necessary distance between manhole covers.
Additional problems arise when the hose or conduit is manually forced into a conduit containing obstacles, obstructions and/or turns. Rigid pipe is not entirely suitable for use in conduits that contain turns because it is difficult to negotiate the pipe through the turns. Likewise, the use of rigid pipe in conduits that contain obstacles or obstructions such as conduit cracks, conduit offsets, roots, collected debris, and other obstructions presents problems because every time the rigid pipe confronts an obstacle or obstruction, it is often necessary to partially withdraw the pipe in attempt to move the pipe around the obstruction. On the other hand, manually forcing flexible or semi-rigid hose into conduits containing turns, obstructions and/or obstacles presents a different set of problems. When a flexible or semi-rigid hose encounters a turn, an obstacle or obstruction, the hose tends to kink or bow, thereby causing the hose to pile up at the point of obstruction or turn.
Another consideration that arises in the treatment of conduits involves the characteristics of the hose commonly used to treat conduits. Typically, the hose is stored on a reel and when it is necessary to treat a conduit, the hose is unwound from the reel and fed into the conduit. The characteristics of the hose commonly used in the treatment of conduits are such that the hose tends to develop a coiled set or memory due to the initial manufacturing process and the fact that the hose is wound on a reel while still hot from the manufacturing process. Consequently, when the hose is unwound from the reel, the hose tends to maintain its coiled shape due to the set or memory that was imparted to the hose when it was manufactured and wound on the reel. The coiled nature of the hose and particularly, the coiled nature of the leading end of the hose, presents many difficulties in attempting to push the hose into the conduit. For instance, rather than pointing in the direction of movement and moving in response to a pushing force, the hose tends to coil on itself and resist the pushing force. Moreover, frictional forces increase as the coiled hose contacts the wall of the conduit.
The alternative methods mentioned above do not involve pushing the hose or pipe through the conduit and consequently, may be better suited in some respects than the aforementioned manual method. However, those alternative methods of jetting and tagging/parachuting are time consuming and are somewhat complex and expensive.